Heating apparatus with removable heating elements and shields

ABSTRACT

The heating elements and heat shields of a vacuum furnace are constructed as a unitary cartridge which may be removed easily from the outer vessel of the furnace to facilitate servicing of the heating elements and the heat shields and to reduce the down time of the furnace. A drive mechanism for advancing workpiece carriers through the furnace also is incorporated into the removable cartridge.

[451 Oct. 10, 1972 United States Patent Bielefeldt HEATING APPARATUS WITH 2,535,379 12/1950 White....................2l9/403 X REMOVABLE HEATING ELEIVIENTS 2,964,389 12/ 1960 Bennett et 1 3/22 X AND SHIELDS 3,160,693 12/1964 Palmer 2,664,490 12/1953 [72] Inventor:

Allgeyer ................219/403 x .....219/403 x Irvin P. Bielefeldt, Loves Park, 111.

2,688,685 9/1954 Goodell Clune et a1.

[73] Assignee: Alco Standard Corporation, Valley Forge, Pa.

Bielefeldt,"...............219/388 22 Filed:

May 6, 1971 Appl. No.: 140,661 Primary Examiner-Volodymyr Y. Mayewsky Attorney-Wolfe, Hubbard, Leydig, Voit & Osann ABSTRACT The heating elements and heat shields of a vacuum furnace are constructed as a unitary cartridge which may be removed easily from the outer vessel of the furnace to facilitate servicing of the heating elements wn time of the furnace. A drive mechanism for advancing workrporated o C O n e i h 0 t. 13 w a u w d a m m u m a d m m h S g M u .m m m m m m e I h n a e m m d m 5 n .1 fl a p 3 3 2% 43 5 4 B/QI i m R2 2M 2 iF M "5 9 Wm MOL .4 2 9" 9/ "3 B, mnw; I B w w 4 .l 2% W5 C In. m m H WC m e m m7 6 m4 fl MM mcM R .9 r W9 3 L 9 01 5 min U IF H m M 5 55 5 UNITED STATES PATENTS into the removable cartridge.

2,522,558 9/1950 Alvarez.................;...219/436 5 Claims, 5 Drawing Figures HEATING APPARATUS WITH REMOVABLE HEATING ELEMENTS AND SHIELDS BACKGROUND OF THE INVENTION This invention relates to a furnace for heating workpieces and, more particularly, to a furnace of the type which includes a vessel defining a chamber within which the workpieces are heated. In such a furnace, radiant heating elements for raising the temperature of the workpieces are disposed in the chamber and are positioned alongside heat shields for concentrating the radiated heat on the workpieces and for restricting heat losses through the walls of the vessel.

SUMMARY OF THE INVENTION The general aim of the present invention is to provide a new and improved furnace of the above character in which the heating elements and heat shields may be cleaned and serviced in a quicker and easier manner than has been possible heretofore with prior furnaces of the same general type. A related object is to provide a furnace which is subject to less down time in the event the heating elements malfunction ancl require repair or replacement.

A more detailed object is to achieve the foregoing by uniquely constructing the heating elements and the heat shields as a unitary cartridge which may be quickly pulled out of the vessel and dipped in a cleaning solution for the purpose of removing accumulated contaminants from the heating elements and heat shields. In addition, if the heating elements are in need of extensive repairs or replacement, the cartridge may be removed from the vessel and replaced with another cartridge even before the furnace has completely cooled thereby to enable operation of the furnace to be resumed quickly and to continue during servicing of the heating elements.

A further object is to provide, as part of the removable cartridge, mechanism for advancing the workpieces into and out of the furnace chamber.

The invention also resides in the novel construction of the cartridge and its manner of attachment to the vessel to close off and seal the heating chamber.

These and other objects and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

' BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially exploded perspective view of a new and improved furnace embodying the novel features of the present invention.

FIG. 2 is a fragmentary cross-section taken through one of the cartridges and showing part of a carrier for the workpieces.

FIG. 3 is a longitudinal cross-section taken vertically through the furnace illustrated in FIG. 1 and along a section line which progresses outwardly from the longitudinal center of the furnace as the section line proceeds from left to right along the furnace.

FIG. 4 is an enlarged fragmentary cross-section taken substantially along the line 4-4 of FIG. 3.

FIG. 5 is a view similar to FIG. 4 but showing the cartridge partially removed from the vessel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the drawings for purposes of illustration, the invention is embodied in a furnace 10 in which metal workpieces 11 (FIG. 1) are heated in the presence of a vacuum to prevent oxides from forming on the surfaces of the workpieces during heating. The workpieces, for example, may comprise aluminum parts which are brazed together in the furnace while a quantity of magnesium is being vaporized in the furnace so as to enable the brazing to be achieved without the use of flux.

In this instance, the workpieces 11 are held in carriers 13 (FIG. 1) which are adapted to be advanced into the furnace one-by-one and in end-to-end relation, each carrier being advanced sequentially into and stopped periodically in three identical heating chambers 14' (FIGS. 3 and 4) disposed end-to-end with one another. The carriers are similar to those described in detail in my U.S. Pat. No. 3,609,295 and each comprises a rectangular window-like frame 15 (FIG. 1) supporting one or more shelves 16 upon which the workpieces rest-Shielding packs 17 (FIG. 2) are attached to the leading and trailing and the upper and lower sides of each carrier and, as explained fully in the aforementioned patent, help promote rapid and uniform heating of the workpieces when the latter are in the chambers.

Prior to and during advancement into the first heating chamber 14, each carrier 13 is supported on an overhead track 19 (FIG. 1) which is disposed within a loading chamber (not shown) located at the left end of the first heating chamber. To suspend the carriers from the track, several hangers 20 (FIG. 2) are attached to the upper side of each carrier and include horizontally extending axles 21 which journal small rollers 23 adapted to ride along the track.

The three heating chambers 14 are defined within three interconnected vessels 24 (FIG. 3) of rectangular cross-section and communicating with one another through open doorways or passageways 25 adjacent the ends of the center vessel. A vacuum pump (not shown) communicates with the center vessel and is operable to establish a high order of vacuum within the heating chambers. The latter are adapted to be sealed tightly by doors 26 housed within door modules 27 located at the outboard ends of the two end, the doors being positioned to close doorways 28 (FIG. 3) in the end vessels.

Heating of the workpieces 11 in each chamber 14 is effected radiantly by electric heating elements 29 (FIGS. 3 and 4) of the resistance type disposed within the chamber. To concentrate the heat from the heating elements on the workpieces and to reduce heat losses through the walls of the vessels 24, heat shields 30 are disposed within each chamber and confine the radiated heat within the area of the workpieces.

In accordance with the primary aspect of the present invention, the heating elements 29 and heat shields 30 within each vessel 24 are constructed as a unitary cartridge 31 (FIGS. 1 and 5) which may be pulled out of the vessel quickly and easily to enable cleaning and repairing of the heating elements and heat shields. Moreover, if the heating elements require extensive servicing, a spare cartridge may be installed in the vessel in place of the cartridge being serviced so as to enable continued operation of the furnace during the servicing period.

More specifically, each cartridge 31 includes a main support which herein is advantageously constituted by a top cover plate 33 (FIG. 1) sized and shaped to close off a large rectangular opening 34 formed in the top wall 35 of each vessel 24. The cover 33 overlies the top wall 35 and is fastened detachably to the latter by a series of bolts 36 (FIG. 2) which serve to draw the cover tightly against a sealing gasket 37 attached to the top wall.

As shown most clearly in FIG. 4, two upright plates 39 are fastened rigidly to opposite side edge portions of each cover 33 and are disposed in the chamber 14 adjacent the side walls of the vessel 24. The heat shields 30 for concentrating the radiated heat on the workpieces II are attached to the side plates 39 and herein comprise a series of side-by-side sheets of reflective heat-resistant material such as lnconel or other nickeliron alloy. The sheets are suitably joined together and are held in spaced apart relation by heat-insulated fasteners 40 which also serve to connect the sheets to the side plates. Preferably, the sheets are arranged with in each vessel 24 to define a shielding enclosure of rectangular cross-section with an open passage or tunnel permitting movement of the workpiece carriers 13 through the vessel. Thus, each of the shields 30 includes upright side sections 41 (FIG. 4) disposed alongside the plates 39 and the side walls of the vessel 24, a bottom section 43 closely adjacent the bottom wall of the vessel, and top sections 44 positioned just above the carriers 13.

In this instance, the heating elements 29 are in the form of vertically extending and horizontally spaced bars spaced inwardly from the inner sides of the side sections 41 of the shields 30 and positioned between the side sections and the carriers 13, there being several heating bars within each chamber 14 (see FIGS. 3 and 4). At their upper and lower ends, the heating bars 29 in each chamber are connected both physically and electrically to upper and lower horizontally extending bus bars 47 which terminate just short of the passageways 25. Each upper bus bar is suspended from conductive hangers 49 which project upwardly through the top sections 44 of the shields 30 and which are connected rigidly to electrical terminals 50 attached to the top cover 33 and adapted to be connected to a source of voltage for energizing the heating bars 29 by way of the bus bars 47. Non-conductive bushings 51 (FIG. 4) are telescoped over the hangers 49 and electrically insulate the latter from the top sections 44 of the shields 30.

It will be apparent from the foregoing that the heating bars 29 and the heat shields 30 in each vessel 24 are suspended entirely from the top cover 33 and are free from connection with the side walls of the vessel. Also, as shown in FIG. 5, the heating bars, the heat shields and'the side plates 39 are located inwardly of the edges of the opening 34 in the top wall 35 of the vessel. Accordingly, by releasing the bolts 36 connecting the cover to the vessel, the cover may be removed from the vessel and, as an incident thereto, the heating bars and the heat shields may be pulled out of the vessel as a unit through the top opening 34 (see FIGS. 1 and 5). With the heating bars and heat shields thus being constructed as an easily removable and unitary cartridge 31, it is a relatively simple matter to gain access to the heating bars for the purpose of repairing the latter. In addition, the cartridge 31 simply may be pulled out of the vessel 24 and dipped into a bath of cleaning solution in order to remove magnesium deposits and other foreign material accumulating on the heating bars and the heat shields during service use. Usually, the cartridges will be handled by an overhead hoist or by a lift truck and will be immersed into the cleaning solution to a depth approximately level with the upper surfaces of the top sections 44 of the heat shields.

A further important advantage resulting from the construction of the heating bars 29 and the heat shields 30 as a unitary cartridge 31 is that the cartridge may be removed from the vessel 24 and replaced with a spare cartridge in the event time-consuming repairs or other servicing are needed. Accordingly, the furnace 10 is subject to less down time and, in addition, it is not necessary to wait for the furnace to cool off completely before switching the cartridges and thus only a comparatively brief interruption in the operation of the furnace occurs during the changeover.

The invention further contemplates incorporating a drive mechanism in each cartridge 31 for advancing the carriers 13 into and out of each vessel 24 along a track 61 (FIG. 4) located in the vessel and attached to the underside of the cover plate 33. Herein, each drive mechanism comprises an endless chain 63 (FIG. 2) trained around sprockets 64 and 65 which are fastened to shaft 66 and 67 joumaled by brackets 69 depending from the cover 33. The chain carries a pair of spaced dogs 70 located to sequentially engage different ones of the axles 21 on the carriers 13 as the chain is driven by a motor 71. Each time one of the motors is energized, one of the dogs 70 on the associated chain 63 advances the carrier until the latter is picked up by one of the dogs on the chain in the succeeding vessel 24.

To advantage, each drive motor 71 is supported on top of the associated cover 33 so as to be protected from the heat in the chamber 14 and to avoid immersion of the motor into the cleaning solution when the lower end portion of the cartridge 31 is dipped into the solution to clean the heating elements 29 and heat shields 30. A gear box 73 (FIG. 2) mounted on top of the cover connects the motor to a vertical shaft 74 extending through the cover and connected by bevel gears 75 to the shaft 67 in order to rotate the sprocket 65 and drive the chain 63 when the motor is energized.

With the drive mechanism 60 being incorporated into the cartridge 31, easy access may be gained to the drive mechanism when the cartridge is removed from the vessel 24. Thus, it is a relatively simple matter to service the drive mechanism as well as the heating elements 29 and the heat shields 30.

I claim as my invention:

1. In a furnace for heating workpieces, the combination of, a vessel having a series of walls defining a work chamber, said vessel having doorways in the ends thereof to accommodate movement of the workpieces into one end of the chamber and out of the other end of the chamber, an opening in the top wall of said vessel, a cover supported on said vessel and closing said opening, a series of electric radiant heating elements suspended from said cover and disposed within said chamber for heating workpieces in the chamber, heat shields suspended from said cover and disposed within said chamber for concentrating the heat from said heating elements on the workpieces and for restricting heat loss through said walls, and means detachably connecting said cover to said vessel whereby said heating elements and said heat shields may be pulled out of said chamber as a unit as an incident to removing said cover from said vessel.

2. A furnace as defined in claim 1 in which said heat shields comprise spaced apart and side-by-side sheets of heat resistant reflective material arranged to define an elongated passageway of generally rectangular cross-section disposed within said chamber and alined with said doorways.

3. A furnace as defined in claim 1 further including carriers for supporting the workpieces in said chamber during heating, and drive mechanism for advancing said carriers into and out of said chamber, said drive mechanism being supported on said cover and being removable from said vessel as a unit with said cover, said heating elements and said heat shields.

4. A furnace as defined in claim 3 in which said drive mechanism comprises a motor supported on the upper side of said cover, a carrier advancing device disposed below and supported by said cover, and means projectthereof to accommodate movement of the workpieces into and out of the chamber and having a passageway alined with the doorways to permit movement of the workpieces through the chamber between the doorways, an opening in the top wall of said vessel a cartridge fitted at least partially into said chamber through said opening, said cartridge comprising (a) a cover supported on said vessel and closing said opening, (b) a series of electric heating elements connected to said cover and disposed within said chamber for heating workpieces in the chamber and (c) heat shields connected to said cover and disposed within said chamber for concentrating the heat from said heating elements on the workpieces and for restricting heat loss through said walls, and means releasably connecting said cover to said vessel whereby the cover may be detached from the vessel and, as an incident to removing the cover from the vessel, said heating elements and said heat shields may be pulled out of said chamber through said opening.

* III l 

1. In a furnace for heating workpieces, the combination of, a vessel having a series of walls defining a work chamber, said vessel having doorways in the ends thereof to accommodate movement of the workpieces into one end of the chamber and out of the other end of the chamber, an opening in the top wall of said vessel, a cover supported on said vessel and closing said opening, a series of electric radiant heating elements suspended from said cover and disposed within said chamber for heating workpieces in the chamber, heat shields suspended from said cover and disposed within said chamber for concentrating the heat from said heating elements on the workpieces and for restricting heat loss through said walls, and means detachably connecting said cover to said vessel whereby said heating elements and said heat shields may be pulled out of said chamber as a unit as an incident to removing said cover from said vessel.
 2. A furnace as defined in claim 1 in which said heat shields comprise spaced apart and side-by-side sheets of heat resistant reflective material arranged to define an elongated passageway of generally rectangular cross-section disposed within said chamber and alined with said doorways.
 3. A furnace as defined in claim 1 further including carriers for supporting the workpieces in said chamber during heating, and drive mechanism for advancing said carriers into and out of said chamber, said drive mechanism being supported on said cover and being removable from said vessel as a unit with said cover, said heating elements and said heat shields.
 4. A furnace as defined in claim 3 in which said drive mechanism comprises a motor supported on the upper side of said cover, a carrier advancing device disposed below and supported by said cover, and means projecting through said cover and operably connecting said motor to said carrier advancing device.
 5. In a furnace for heating workpieces, the combination of, a vessel having a series of walls defining a work chamber, said vessel having doorways in opposite ends thereof to accommodate movement of the workpieces into and out of the chamber and having a passageway alined with the doorways to permit movement of thE workpieces through the chamber between the doorways, an opening in the top wall of said vessel a cartridge fitted at least partially into said chamber through said opening, said cartridge comprising (a) a cover supported on said vessel and closing said opening, (b) a series of electric heating elements connected to said cover and disposed within said chamber for heating workpieces in the chamber and (c) heat shields connected to said cover and disposed within said chamber for concentrating the heat from said heating elements on the workpieces and for restricting heat loss through said walls, and means releasably connecting said cover to said vessel whereby the cover may be detached from the vessel and, as an incident to removing the cover from the vessel, said heating elements and said heat shields may be pulled out of said chamber through said opening. 